This invention concerns a supply air terminal designed for installation in an opening in a wall of a ventilation duct, which supply air terminal extends in the duct with a part shaped to be able to take up part of the air flow transported in the duct and transport this for venting outside the ventilation duct.
In order to achieve a supply of air inside buildings and rooms, storage premises and other large areas therein, it is usual to use supply air terminals, for example nozzles, grilles, air directing valves, etc., installed directly in, for example, rectangular or spiral flanged ducts. These ventilation ducts form a ventilation duct system comprising a main duct and a number of branch ducts through which an air distribution takes place. A fan is arranged at the start of this system in order to generate an air pressure.
Current technology suffers in general from the disadvantage that while the ducts in the ventilation duct system closest to the fan device are subject to a pressure many times greater than the system""s ducts located further away from the fan device, the abovementioned nozzles or other grille arrangements for supply air must be placed in the branch ducts and not in the main duct. The known supply air terminals are installed together with a pressure reducing valve and sound dampers, which results in increased installation and operating costs and generally creates an unaesthetic interior design impression. Supply air grilles according to current technology create troublesome noise levels at relatively low drops in pressure.
It is desirable to eliminate pressure-reducing valves and sound dampers in the ventilation duct system by means of a supply air terminal which maintains a static overpressure and creates a laminar air flow, which supply air terminal is able to be installed directly in the main duct and/or branch ducts.
Current technology lacks flexibility in the installation of grille devices, as these must have different grille sizes and lamella designs.
Supply air devices according to current technology must in addition be provided with distribution valves or flap valves, which further complicate their use. Designs of such elements which are in use today contain a number of moving parts which can break. Similarly, the surface where a hole needs to be made for known ventilation devices has a relatively large extent over the surface of the casing of the duct which affects the durability of the ventilation ducts.
The grille and the valve according to current technology mean that the pressure must be reduced at the connection of the branch duct to the main duct. This is not desirable as grilles according to current technology cannot bridge pressure differences without creating noise.
Supply air devices according to current technology can also consist of a number of smaller nozzles which are placed individually in the wall of the ventilation duct. The number of nozzles is determined by the required air flow, which can result in a very large number of nozzles, with increased costs as a result This provides a certain drop in pressure but no laminar flow. Similarly, the installation of the abovementioned nozzles is complicated and expensive.
The aim of the invention is to eliminate the use of pressure-reducing valves and sound dampers in the ventilation duct system, by providing a supply air terminal which can be installed directly in the main duct and/or branch ducts.
A second aim is to provide a supply air terminal which in its internal part creates a laminar flow in order to be able to achieve long projections.
The aim is also to provide a supply air terminal which is cheap to manufacture and install. The supply air terminal must also provide a unobtrusive impression where interior design is concerned.
The invention further aims to provide a supply air terminal which can be mass-produced simply and cheaply in a few sizes. This supply air terminal must also allow good flexibility when being installed in a ventilation duct system, for example in a room in a building.
The above mentioned problems are solved by means of a supply air terminal of the type described in the introduction where part of the supply air terminal has a considerable extent in the ventilation duct in order to achieve a drop in pressure and also a laminar flow in the supply air terminal.
The extent inside the ventilation duct amounts to 60-90% of the internal diameter of the ventilation duct, which generally means that approximately 8% of the cross sectional area of the ventilation duct is taken up by the part of the terminal in the ventilation duct.
The terminal is provided with a slot-shaped duct, which extends in the longitudinal direction of the ventilation duct.
The cross section can for example, be drop-shaped or elliptical. The part of the terminal inside the duct can also be shaped so that a laminar air flow arises at the place where the air is forced into the terminal. This aerodynamic design can be achieved by means of current technology.
An internal duct in the terminal can also be designed so that it widens out towards the opening in the wall of the ventilation duct. That is to say that the cross section of the internal duct, viewed in the longitudinal direction of the ventilation duct, can have a trapezoid shape, which means that the air velocity is reduced so that the static pressure is maintained and the projection is reduced.
The invention means that a supply air terminal is produced which, with its simplified construction, creates a pressure reduction and a laminar flow in the supply air, which supply air terminal is simple and cheap to manufacture and allows flexibility when installing a ventilation duct system.
The invention also means that one or more terminals can be installed in the main duct without branch ducts and sound dampers needing to be used. This results in reduced manufacturing and installation costs.
In addition, the invention makes it possible to use the same size terminal throughout the whole ventilation system, where normally the ventilation ducts have a smaller diameter the further they are from the source generating the pressure. Reduction in pressure and laminar flow are achieved using the invention regardless of where in the system the terminal is situated. A number of terminals, for example installed in succession, can provide a larger air flow, dependent upon the air changes required.
The invention thus means that the supply air terminal only needs to be manufactured in a few sizes, that is to say a supply air terminal which can be installed simply using different types of inserts to give the supply air terminal the required characteristics, regardless of where it is situated in the ventilation duct system. The supply air terminal can be placed singly or in groups directly in the main duct. This means that a supply air terminal is achieved which can be mass-produced in a few sizes and can be provided with inserts as required. Where long projections are required, for example in large storerooms, the terminal can be installed in the ventilation duct horizontally with the ceiling of the room and not provided with any insert, as a laminar flow is obtained without such insert. If the supply air is required to have a turbulent flow, the terminal can be provided with inserts of various kinds. For example the insert can have a dispersion pattern where the supply air has a fan-shaped dispersion or as projected in a conical pattern.